1. Field of the Invention
The present invention relates to medical devices for repairing injured nerves, and more particularly to a device and method for the repair of a severed peripheral nerve.
2. Discussion of the Prior Art
The repair of lacerated or severed peripheral nerves using sutures is a common surgical procedure known as neurorrhaphy. The use of this sophisticated technique in recent years has enhanced the surgeon's ability to reattach amputated body parts, to achieve composite tissue transfer, and to graft nerves. The success of such procedures is still limited because the current methods of suturing severed nerves is difficult, time-consuming, and often yields poor functional results due to a variety of factors. The replanting of amputated fingers and limbs is especially limited by poor nerve regeneration.
One such factor is the tendency of severed nerve ends to contract and pull apart after suffering damage. Consequently, when reconnection of the nerves is attempted, a tensile force may be created in the severed ends as they are drawn together, complicating both the process of rejoining the severed ends, and the healing process. In conventional surgery using a microsuture, it is difficult to retain the severed nerve ends in approximation while they are being reconnected peripherally around the epineurium with the suture. During the healing process it is also difficult to deter the tensile force created in the severed nerve ends from causing the ends to pull loose from their stitched reconnection, thus leading to poor functional reconnection of the nerve.
In one approach to promoting nerve regeneration, as disclosed in U.S. Pat. No. 4,778,467, an epineural or endoneurial monosuture is used to hold the nerve ends in close proximity, where they are enclosed by a tubular prosthesis which tightly seals the injured nerve to isolate it from the rest of the body of the host. The monosuture is formed by introducing a long needle carrying a very fine suture thread through the perineurium of the injured nerve, and drawing the monosuture and needle through the interior of the distal nerve end and into the interior of the proximal nerve end. The needle and thread are thereupon withdrawn from the proximal nerve end through the perineurium of the injured nerve. Tension applied to the monosuture brings the nerve ends into close proximity, so that the nerve ends are in contact with each other, and the ends of the monosuture are knotted. However, this device has the inherent disadvantage of preventing the surgeon from observing the anastomotic site to ascertain correct rotational alignment after enclosure of the anastomotic site with the tubular prosthesis.
Another approach seeks to protect the anastomotic site by encasing it. U.S. Pat. No. 4,883,618 shows a medical device for the sutureless repair of damaged nerves comprising longitudinally openable tubes of a body-absorbable polymer. The damaged nerve is positioned therein longitudinally without the need of suturing. The nerve purportedly becomes bonded to the porous surface of the tube so that the two portions need not be lashed together with a suture.
Another approach to sutureless tubulation involves sucking the nerve stumps into a porous metallic tube by means of a vacuum actuated instrument as disclosed in U.S. Pat. Nos. 3,916,805 and 3,960,151. However, this method risks compressive injury to the nerve upon post-surgical swelling in addition to the disadvantage of preventing the surgeon from observing the anastomotic site to ascertain correct rotational alignment.
An alternative to direct suturing is by laser fusion. Theoretical investigations into the use of an argon laser, as disclosed by E. R. Campion et al., Repair of Peripheral Nerves with the Argon Laser, The Journal of Bone and Joint Surgery, Incorporated (1990), have indicated in experiments involving rabbits that it is possible to allow sealing of the epineurium without thermal damage to adjacent neural tissue. However, one problem with this alternative lies in the difficulty of retaining the severed ends in close apposition while the epineurium is sealed together with the laser. Despite the progress in this area, Campion acknowledges that repair with microsuture remains the standard against which any alternative must be measured.
In the prior approaches outlined above, it is still difficult to hold the severed ends of the damaged nerve together and aligned, both during surgery and healing. Despite attempts to align proximal and distal segments of the nerve, there is a tendency for the regenerating proximal axons to sprout outside their fascicular and epineural confines. This leads to formation of neuromas and consequent incomplete reinnervation.
Thus, repairing severed nerves remains a long-standing problem that continues to plague surgeons. Despite the advances in microsurgical techniques, a patient's recovery from a serious wound is often limited by the degree of nerve damage that cannot be repaired using current technology. The present invention provides devices and methods which help to avoid the aforementioned disadvantages.